As "stand-alone" devices, portable computers usually have limited facilities for connection to other devices (displays, stores, printers, communication links, etc.). Expansion (or "docking") units (or "boxes" or "modules"), to which the portable computers can optionally attach, provide extended resources for that purpose. A typical docking unit could include extended power resources and connection facilities permitting respective portable units to be attached to many types of devices not otherwise accessible to such computers.
Contemporary personal computers, including many portable computers, have built-in serial port, parallel port, and modem (or telephone jack) connectors, and internal circuitry effectively enabling the user to selectively assign one of a plurality of com x internal logical signal paths (x=1, 2, etc.) to each connector and to associated devices attached externally to the connector. being referred to as "com 1" and "com 2".
A problem presented relative to dockable portable computers is that devices in the paired portable and docking units may be given overlapping and/or potentially conflicting communication port assignments, and in such circumstances it would be unwieldy to require the user to adjust these assignments each time the portable unit is attached to and detached from the docking unit.
In some computer systems, states of device attachments, including com x path assignments, are stored in a non-volatile (CMOS) memory and reestablished automatically each time that the computer is powered up. However, these known path assignment arrangements are limited in the sense that they condition automatic reassignment of paths on a "polling" of device identities, so that if the identity received from a given device location does not match the associated content of the non-volatile memory user intervention is required.
For example, in IBM PS/2 Personal Computer Systems which have Micro Channel buses (IBM, PS/2 and Micro Channel are trademarks of the International Business Machines Corporation), device path assignments are automatically reestablished at power up by an automatic Program Option Select Process described in pending U.S. Pat. application by C. E. Heath et al. (Ser. N. 07/296,387, now U.S. Pat. No. 5,038,320, filed Jan. 6, 1989). In this process, known addresses are polled for device identities and responses are compared to identity values stored in a non-volatile memory. If the comparison indicates that devices currently installed (memory, disk drives, optional feature cards, etc.) are the same as those present when the system was last powered up, device configurations (including com path assignments if appropriate) are reestablished automatically by transfer of associated configuration information from the non-volatile memory. However, if the installation has changed, the user must install a special diskette and run the system through a reconfiguring process.
Obviously, it would be unwieldy to require a user of a dockable portable computer to act in this manner each time that the system is initialized in a stand-alone mode after being previously docked, or initialized in a docked mode after being previously used in a stand-alone mode.
The present invention provides an automatic power-up initialization process for such dockable systems which can function without user intervention, even when potentially conflicting com x path assignments have been made relative to the portable unit and its associated docking station.